Glyn Jones, Chairman of the Board of Directors, said: "Since Endurance
publicized its letter to Aspen on 14th April, we have
actively reached out to shareholders and have found overwhelming
consensus for our rejection of Endurance's ill-conceived 'proposal,'
which undervalues Aspen, represents a strategic mismatch and carries
significant execution risk. Furthermore, our discussions with clients
and brokers have confirmed our view that the combination would result in
substantial dis-synergies. Mr. Charman's characterizations are merely an
attempt to deflect from the real point that the 'proposal' is
unattractive and not actionable."

As you are undoubtedly aware, the Board of Directors of Aspen Insurance
Holdings Limited believes that the transaction that Endurance Specialty
Holdings Ltd. seeks with Aspen - first indicated in its 18th
February letter, repeated again in its 3rd April letter and
then repeated publicly on 14th April - is not in the best
interests of Aspen or its shareholders. Since Endurance publicized its
letter on 14th April, we have been in touch with a number of
you, as well as a number of our clients and brokers, and have found
overwhelming consensus for our rejection of Endurance's "proposal."

We have repeatedly informed Endurance of our serious concerns regarding
its "proposal," but Endurance has failed to respond substantively to any
of them. These concerns include:

Endurance significantly undervalues Aspen's business

The Aspen Board has concluded that Aspen will be able to create superior
value for Aspen shareholders based on our standalone plan. We have built
a diversified business with a clear strategy, strong balance sheet,
proven management team and disciplined risk management, and are
confident that continued execution of our strategy provides value far in
excess of what is suggested in a risky combination with Endurance. In
that regard, the investments we have made in our Lloyd's business and US
Insurance business are on track to fulfill our expectations, and we
expect our book value to increase meaningfully as a result. We are very
focused on executing on our clear strategy for building superior value
for you.

Endurance stock as consideration in a combination is not appealing

Endurance has an unattractive business mix and quality of earnings
issues. A combination with Endurance would cause Aspen and its
shareholders to suffer from the difficulties attributable to Endurance's
business, including: (1) its over-reliance on crop insurance, a business
which is troubled, low-margin, recently volatile and exposed to major
risks, (2) the lack of progress in its other insurance businesses, which
are in a nascent stage and (3) its weak reinsurance business. Moreover,
Endurance's earnings in recent years have been driven disproportionately
by prior-year reserve releases. The combination Endurance proposes is,
in our view, an effort by Endurance to solve its business issues at the
expense of Aspen and its shareholders.

There are substantial risks regarding the supposed synergies.
Endurance claims that a combination would result in "over $100 million
of annual synergies," but its discussion is superficial, its claims are
unsubstantiated and the types and sources of synergies are unidentified.
Importantly, we believe this claim assumes no disruption or loss of
business to the combined company. Based on what we are hearing from
clients and brokers so far, our serious concerns about the potential
combination's dis-synergies, as indicated in our letter of 8th
April, are on target. If anything, we appear to have understated the
dis-synergies and the impact they would have on the value of the
combined company. Scale for the sake of scale is not a reason to pursue
a business combination with Endurance.

The CVC investment will negatively impact the shareholders of both
companies. Endurance states that CVC's $1.05 billion investment
consists of Endurance shares at a "pre-negotiated discount," Endurance
warrants with an exercise price "higher than an average market price"
and "customary" governance rights for a "significant" minority
investment. The amount of equity to be given up to CVC and at what
"discount[ed]" price, the amount and terms of the warrants and the
"customary" governance rights that CVC would receive all significantly
impact the economics of a potential transaction - not just for Aspen and
its shareholders, but for Endurance and its shareholders as well. These
terms are extremely important to the valuation of the stock component of
the consideration that Endurance proposes. If answers to these questions
are in fact known, the information should be disclosed to Endurance's
own shareholders and the market as a whole.

Endurance has expressed a strong dislike for Lloyd's business. In
an attempt to convince the market that Endurance would embrace Aspen's
top tier Lloyd's business, John Charman, Chairman and Chief Executive
Officer of Endurance, stated on 14th April that "Aspen's core
strength in the London insurance market - including through Lloyd's - is
an attractive area." This is in stark contrast to Endurance's previously
expressed disdain for Lloyd's, including less than a year ago when Mr.
Charman stated, "I find it difficult to want to be a . . . piece of
[Lloyd's]." (Insurance Insider, 10th June 2013). Given
such statements, we would be extremely concerned that a combination with
Endurance would pose risks to our Lloyd's syndicate, which is one of the
most dynamic parts of our insurance franchise and a top performer
amongst Lloyd's syndicates.

The availability of the cash consideration is highly uncertain

Endurance states that the CVC "commitment," which constitutes most of
the cash Endurance would use in a transaction, is "subject to customary
due diligence of Aspen by the investors." Endurance's response to the
concerns we noted in our 8th April letter regarding the
certainty of CVC's "commitment" - that it will provide the terms of the
commitment only if we sign a non-disclosure agreement and sit down to
meet with Endurance - is no answer at all. Either Endurance has the
funds or it does not, and if it has the funds, it should say so. The
financing commitment letter should be fully disclosed publicly.

We would expect material personnel disruption and loss of business
due to the cultural mismatch between the two companies

We have serious concerns about the significant personnel disruption and
loss of attractive business that would result from a combination of
Aspen's collaborative, teamwork-oriented culture with Endurance's
centralized, top-down management model. Endurance's recent description
of its "collegial environment" is inconsistent with the industry's
experience. Aspen is currently in litigation as a result of Endurance's
orchestrated poaching of Aspen employees, and, according to news
reports, Mr. Charman was relieved of his positions at his last two
companies for his less than collegial attitude - reportedly leaving ACE
due to "personal differences" and AXIS when the "board kicked him out in
2012 without cause." (SNL Insurance Daily, 23rd August
2013). Yet, now Endurance assures our and its own shareholders that a
business where the most valuable assets are its people will thrive, and
that the merging of the two cultures will proceed smoothly, in the
"collegial environment" established under Mr. Charman's leadership.

Endurance's "proposal" is highly conditional

Endurance's "proposal" is merely a request for a one-way option to start
an investigation of our company and then later decide if it wishes to
pursue a transaction. In addition to the transaction being subject to
due diligence of Aspen by Endurance, Endurance's financing sources would
similarly require due diligence of Aspen and would later decide whether
or not they wanted to provide the necessary cash funding to Endurance.
Furthermore, in addition to a number of regulatory approvals, the
transaction described by Endurance would be subject to the approval of
both Aspen's and Endurance's shareholders - such approvals being sought
for a transaction where there would be economically dilutive
sponsor-financing and warrants issued of an undisclosed amount and
undisclosed value.

The foundation of Aspen's business is our client relationship franchise,
and our people are our most valuable asset. The Aspen Board of Directors
is vehemently opposed to the hostile attempt of Endurance to address its
business problems at the expense of Aspen and its shareholders. Our
Board takes very seriously its fiduciary obligation to pursue all
credible offers that have the potential to create superior shareholder
value, and we have carefully and thoroughly evaluated Endurance's
"proposal." For all the reasons indicated in this letter and our prior
letter to Endurance, we are resolute that Endurance's proposal is not in
your best interests.

Sincerely,

/s/

/s/

Glyn Jones

Chris O'Kane

Chairman of the Board of Directors

Chief Executive Officer

- ENDS -

About Aspen Insurance Holdings Limited

Aspen provides reinsurance and insurance coverage to clients in various
domestic and global markets through wholly-owned subsidiaries and
offices in Bermuda, France, Germany, Ireland, Singapore, Switzerland,
the United Kingdom and the United States. For the year ended December
31, 2013, Aspen reported $10.2 billion in total assets, $4.7 billion in
gross reserves, $3.3 billion in shareholders' equity and $2.6 billion in
gross written premiums. Its operating subsidiaries have been assigned a
rating of "A" ("Strong") by Standard & Poor's, an "A" ("Excellent") by
A.M. Best and an "A2" ("Good") by Moody's.

Application of the Safe Harbor of the Private Securities Litigation
Reform Act of 1995

This press release may contain written "forward-looking statements"
within the meaning of the U.S. federal securities laws. These statements
are made pursuant to the safe harbor provisions of the Private
Securities Litigation Reform Act of 1995. Forward-looking statements
include all statements that do not relate solely to historical or
current facts, and can be identified by the use of words such as
"expect," "intend," "plan," "believe," "project," "anticipate," "seek,"
"will," "likely," "estimate," "may," "continue," "deliver," and similar
expressions of a future or forward-looking nature.

All forward-looking statements rely on a number of assumptions,
estimates and data concerning future results and events and are subject
to a number of uncertainties and other factors, many of which are
outside Aspen's control that could cause actual results to differ
materially from such statements.

Forward-looking statements do not reflect the potential impact of any
future collaboration, acquisition, merger, disposition, joint venture or
investments that Aspen may enter into or make, and the risks,
uncertainties and other factors relating to such statements might also
relate to the counterparty in any such transaction if entered into or
made by Aspen.

Aspen believes these factors include, but are not limited to: our
ability to successfully implement steps to further optimize the business
portfolio, ensure capital efficiency and enhance investment returns; the
possibility of greater frequency or severity of claims and loss
activity, including as a result of natural or man-made (including
economic and political risks) catastrophic or material loss events, than
our underwriting, reserving, reinsurance purchasing or investment
practices have anticipated; the assumptions and uncertainties underlying
reserve levels that may be impacted by future payments for settlements
of claims and expenses or by other factors causing adverse or favorable
development; the reliability of, and changes in assumptions to, natural
and man-made catastrophe pricing, accumulation and estimated loss
models; decreased demand for our insurance or reinsurance products and
cyclical changes in the highly competitive insurance and reinsurance
industry; changes in insurance and reinsurance market conditions;
increased competition from existing insurers and reinsurers and from
alternative capital providers and insurance-linked funds and
collateralized special purpose insurers on the basis of pricing,
capacity, coverage terms, new capital, binding authorities to brokers or
other factors and the related demand and supply dynamics as contracts
come up for renewal; changes in the availability, cost or quality of
reinsurance or retrocessional coverage; changes in general economic
conditions, including inflation, deflation, foreign currency exchange
rates, interest rates and other factors that could affect our financial
results; the risk of a material decline in the value or liquidity of all
or parts of our investment portfolio; evolving issues with respect to
interpretation of coverage after major loss events; our ability to
adequately model and price the effect of climate cycles and climate
change; any intervening legislative or governmental action and changing
judicial interpretation and judgments on insurers' liability to various
risks; the effectiveness of our loss limitation methods, including our
reinsurance purchasing; changes in the total industry losses, or our
share of total industry losses, resulting from past events and, with
respect to such events, our reliance on loss reports received from
cedants and loss adjustors, our reliance on industry loss estimates and
those generated by modeling techniques, changes in rulings on flood
damage or other exclusions as a result of prevailing lawsuits and case
law; the impact of one or more large losses from events other than
natural catastrophes or by an unexpected accumulation of attritional
losses; the impact of acts of terrorism, acts of war and related
legislation; any changes in our reinsurers' credit quality and the
amount and timing of reinsurance recoverables; the continuing and
uncertain impact of the current depressed lower growth economic
environment in many of the countries in which we operate; the level of
inflation in repair costs due to limited availability of labor and
materials after catastrophes; a decline in our operating subsidiaries'
ratings with S&P, A.M. Best or Moody's; the failure of our reinsurers,
policyholders, brokers or other intermediaries to honor their payment
obligations; our ability to execute our business plan to enter new
markets, engage in acquisitions or introduce new products and develop
new distribution channels, including their integration into our existing
operations; our reliance on the assessment and pricing of individual
risks by third parties; our dependence on a few brokers for a large
portion of our revenues; the persistence of heightened financial risks,
including excess sovereign debt, the banking system and the Eurozone
debt crisis; changes in our ability to exercise capital management
initiatives (including our share repurchase program) or to arrange
banking facilities as a result of prevailing market changes or changes
in our financial position; changes in government regulations or tax laws
in jurisdictions where we conduct business; changes in accounting
principles or policies or in the application of such accounting
principles or policies; Aspen or Aspen Bermuda Limited becoming subject
to income taxes in the United States or the United Kingdom; loss of one
or more of our senior underwriters or key personnel; our reliance on
information and technology and third party service providers for our
operations and systems; and increased counterparty risk due to the
credit impairment of financial institutions.

For a detailed description of uncertainties and other factors that could
impact the forward-looking statements in this press release, including
the positioning to deliver profitable growth and value for investors,
please see the "Risk Factors" section in Aspen's Annual Report on Form
10-K for the year ended December 31, 2013, filed with the U.S.
Securities and Exchange Commission on February 20, 2014. Aspen
undertakes no obligation to update or revise publicly any
forward-looking statements, whether as a result of new information,
future events or otherwise.